Buried structure detection device

ABSTRACT

An underground buried object detecting apparatus has a capacitance sensor attached to a base plate to be faced to the ground, to detect an underground capacitance change, a stored value of a reference capacitance corresponding to the absence of a buried object, a comparing operation device for comparing detected capacitance with the stored capacitance value, and a buzzer for receiving a signal from the operation device and indicating presence of a buried object.

TECHNICAL FIELD

The present invention relates to an underground buried object detectingapparatus to detect underground buried objects such as mines accordingto capacitance changes.

BACKGROUND TECHNOLOGY

A conventional underground buried object detecting apparatus isdisclosed in, for example, Japanese Unexamined Patent ApplicationPublication No. 2000-266843. This conventional underground buried objectdetecting apparatus is a mine detector having an underground probingradar that employs electromagnetic waves to detect mines buriedunderground. This mine detector can detect mines with electromagneticwaves at high accuracy.

The above-mentioned conventional mine detector, however, employselectromagnetic waves to limit the material of detectable mines. It hasa problem of incapability of detecting mines made of, for example,resin.

It has another problem that it cannot be used for mines that are formedto explode in response to electromagnetic waves.

DISCLOSURE OF INVENTION

A first object of the present invention is to provide an undergroundburied object detecting apparatus capable of correctly detecting targetburied objects irrespective of the material of the target buried objectsto detect. A second object thereof is to provide an underground buriedobject detecting apparatus that is effectively usable for mines thatexplode in response to electromagnetic waves.

To achieve the objects of the present invention, there is provided anunderground buried object detecting apparatus having a capacitancesensor attached to a base plate to be faced to the ground, to detect anunderground capacitance change, reference value storing means forprestoring a reference capacitance according to a capacitance changewhen no target buried object is present in the ground, operation meansfor comparing the detected capacitance change with the storedcapacitance and detecting the presence of a target buried object in theground, and information means for receiving a signal from the operationmeans and informing of the presence of the target buried object.

The capacitance sensor includes a measuring electrode and a groundelectrode each made of an annular conductive metal plate concentricallyarranged on a bottom face of the base plate.

Further, the capacitance sensor has integral terminals passing throughthe base plate. The terminals are electrically connected to a circuitarranged on a top face of the base plate.

On the bottom face of the base plate, a nonconductive resin material isarranged to cover the capacitance sensor.

The information means is a buzzer to receive the signal from theoperation means and inform of the presence of the target buried objectwith a warning sound.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing an underground buried objectdetecting apparatus according to an embodiment of the present invention;

FIG. 2 is a side view showing essential parts and a relationship betweena detecting part and the ground according to the embodiment;

FIG. 3 is a partly broken enlarged view showing essential parts of thedetecting part;

FIG. 4 is a bottom view showing a base plate according to theembodiment;

FIG. 5 is an enlarged sectional view showing essential parts accordingto the embodiment;

FIG. 6 is a block diagram showing a controller according to theembodiment;

FIG. 7 is a graph showing capacitance changes according to theembodiment; and

FIG. 8 is a block diagram showing a controller according to a modifiedembodiment of the present invention.

BEST MODE OF IMPLEMENTATION

FIG. 1 is a perspective view showing a mine detector as an embodiment ofan underground buried object detecting apparatus of the presentinvention. The mine detector 1 of FIG. 1 has a handling part 3 and adetecting part 5.

The handling part 3 includes support rods 7 a and 7 b and handling rods9 a and 9 b. The support rods 7 a and 7 b consist of pipes made of lightmetal such as aluminum, resin, etc. One support rod 7 b is provided withan operation box 11. The operation box 11 accommodates a power sourceconsisting of a small battery, a fuel cell, or a fuel battery, etc. Onthe surface of the operation box 11, there are operation buttons 13 aand 13 b to operate ON/OFF switches. The ON/OFF switches are connectedto the power source in the operation box 11.

The handling rods 9 a and 9 b consist of pipes made of light metal suchas aluminum, resin, etc., and are fitted and fixed to rear ends of thesupport rods 7 a and 7 b. Rear ends of the handling rods 9 a and 9 b areprovided with arm rests 15 a and 15 b made of light metal such asaluminum, resin, etc.

The handling part 3 may be provided with a shoulder part to be hung fromand supported by the shoulder of a worker. In this case, a balancer maybe arranged to balance with the weight of the handling part 3 anddetecting part 5 on each side of the worker. When the shoulder part ishung on the shoulder of the worker, the balancer may balance with theweight of the handling part 3 and detecting part 5, so that thedetecting part 5 may stably face the ground.

The details of the detecting part 5 will be explained with reference toFIGS. 2 to 5. FIG. 2 is a side view showing a relationship between thedetecting part 5 and the ground 17, FIG. 3 is a partly broken enlargedside view partly showing the detecting part 5, FIG. 4 is a bottom viewshowing a base plate, and FIG. 5 is an enlarged sectional view showingessential parts.

In FIG. 2, the detecting part 5 keeps a height H=30 mm to 40 mm from theground 17, to detect a target buried object 19. According to thisembodiment, the target buried object 19 is a mine. The height H isoptionally selectable depending on a sensing capacity. The detectingpart 5 has a housing 21 and a head part 23.

The housing 21 is made of, for example, aluminum and is formed in atruncated conical shape. The head part 23 is made of, for example,aluminum and is fixed to a top face of the housing 21 with screws,adhesive, etc. To the head part 23, front ends of the support rods 7 aand 7 b are fixed with, for example, screws through a flange.

At a lower end of the housing 21, a flange part 25 is circumferentiallyarranged as shown in FIG. 3. At the lower end of the housing 21, thebase plate 27 is arranged. The base plate 27 has a disk shape as shownin FIG. 4. An outer periphery thereof is provided with a plurality ofthrough holes 28 for fastening at given intervals. The outer peripheryof the base plate 27 abuts against the flange part 25 of the housing 21.

The base plate 27 is faced to the ground 17. A bottom face thereof isprovided with a capacitance sensor 29 to detect a capacitance change inthe ground. The capacitance sensor 29 consists of a conductive metalthin plate made of, for example, copper and includes a measuringelectrode 31 and a ground electrode 33. These electrodes are annular andare concentrically arranged on the bottom face of the base plate 27. Themeasuring electrode 31 and ground electrode 33 may consist of conductivemetal foils made of, for example, copper.

The measuring electrode 31 and ground electrode 33 of the capacitancesensor 29 are provided with integral terminal parts 35 and 37 as shownin FIG. 5. The terminal parts 35 and 37 rise toward the base plate 27,pass through the through holes 39 and 41 formed in the base plate 27,and protrudes from the top face of the base plate 27. On the top face ofthe base plate 27, a circuit 43 is formed by, for example, printing. Theterminal parts 35 and 37 are electrically connected to the circuit 43by, for example, soldering.

On the bottom face of the base plate 27, a resin plate 45 made ofnonconductive resin material is fitted to cover the measuring electrode31 and ground electrode 33 of the capacitance sensor 29. The resin plate45 has a disk shape whose diameter is the same as that of the base plate27.

The base plate 27 and resin plate 45 are laid on the flange part 25 ofthe housing 21, and they are fastened and fixed together with fasteningmembers 47 such as rivets, bolts and nuts, etc., at givencircumferential intervals. Instead of the resin plate 45, the bottomface of the base plate 27 may be covered with a resin mold.

The top face of the base plate 27 is provided with a controller 49. Thecontroller 49 is electrically connected to the circuit 43 mentionedabove. The controller 49 is connected to a signal line 51 and a powersource line 53. The signal line 51 is connected to a buzzer 55 servingas a information unit arranged in the head 23. The power source line 53is passed through the housing 21, the head part 23, the support rod 7 b,and the ON/OFF switches in the operation box 11 and is connected to apower source.

In the head part 23, the buzzer 55 is fixed to the top face of thehousing 21 with, for example, screws. The buzzer 55 is connected to apower source line 57, which is passed through the support rod 7 b andthe ON/OFF switches in the operation box 11 and is electricallyconnected to the power source.

The controller 49 is formed as shown in the block diagram of FIG. 6. Thecontroller 49 has the capacitance sensor 29, an oscillating circuit 59,a frequency voltage converting circuit 61, an A/D converting circuit 63,and an MPU 65. The controller 49 is connected to the buzzer 55 through adriving circuit 67.

The MPU 65 prestores a reference capacitance according to a capacitancechange when the target buried object 19 is not in the ground. Namely,according to the embodiment, the MPU 65 forms the reference valuestoring means. The MPU 65 compares a detected capacitance change withthe stored capacitance change and detects the presence of the targetburied object 19 in the ground. Namely, according to the embodiment, theMPU 65 also forms the operation means.

In an underground buried object detecting work, the ON operation button13 a is pushed to activate the detector. Then, a worker puts his or herelbows on the arm rests 15 a and 15 b, grasps the handling rods 9 a and9 b, sets the detecting part 5 on the ground 17 at a distance H=30 mm to40 mm as shown in FIG. 2, and starts the work.

If the capacitance sensor 29 detects a capacitance change, theoscillating circuit 59 provides a frequency change corresponding to thecapacitance change to the frequency voltage converting circuit 61. Thefrequency voltage converting circuit 61 converts the input frequencychange into a voltage change and provides the voltage change to the A/Dconverting circuit 63. The A/D converting circuit 63 converts the inputvoltage change into a binary digital signal and provides the signal tothe MPU 65. The MPU 65 compares the input detected capacitance changewith the stored reference capacitance change.

According to a result of the comparison, the MPU 65 detects the presenceof the target buried object 19 such as a mine as shown in FIG. 2 andprovides an output to the driving circuit 67. Then, the driving circuit67 provides an output signal to the buzzer 55, which is activated togenerate a warning sound that informs of the presence of the targetburied object 19. In this way, the worker can correctly detect thepresence of the target buried object 19 in the ground 17.

After the completion of the work, the OFF operation button 13 b ispushed to inactivate the underground buried object detecting apparatus1.

FIG. 7 is an exemplary graph showing the capacitance changes mentionedabove. An abscissa of FIG. 7 represents time t and an ordinate indicateschanges in capacitance ε. ε1 is a capacitance change when the targetburied object 19 is not in the ground 17. If the target buried object 19is present, capacitance increases as indicated with εs and reaches toε2. Accordingly, the MPU 65 sets a reference capacitance ε2 based on ε1and prestores the same. When the detected capacitance change εs exceedsthe reference capacitance ε2, the target buried object 19 will bedetected. Namely, when the detected capacitance εs exceeds the referencecapacitance ε2, the MPU 65 provides an output signal to the drivingcircuit 67, which activates the buzzer 55.

The setting of the reference capacitance ε2 may depend on the kind ofthe target buried object 19. It is also possible to find the kind of thetarget buried object 19 based on an inner area surrounded by thecapacitance change εs and a state of the capacitance change εs.

In this way, the detecting apparatus can detect the presence of thetarget buried object 19 according to a capacitance change, andtherefore, is capable of correctly detecting the target buried object 19even if it is, for example, a mine made of resin.

Even if the target buried object 19 is a mine that detonates in responseto electromagnetic waves, the mine detector 1 according to theembodiment can correctly detect the same without detonating it becausethe mine detector 1 of the embodiment employs a capacitance change fordetection.

The capacitance sensor 29 consists of the measuring electrode 31 andground electrode 33 each made of an annular conductive metal thin plateconcentrically arranged on the bottom face of the base plate 27. Byfacing the base plate 27 to the ground and by optionally moving the samerelative to the ground in back, forth, left, and right directions, thedetector can correctly detect a capacitance change ε in the ground andcan find the target buried object 19 at high precision.

The capacitance sensor 29 integrally has the terminal parts 35 and 37passing through the base plate 27. The terminal parts 35 and 37 areelectrically connected to the circuit 43 arranged on the top face of thebase plate 27. As a result, the capacitance sensor 29 arranged on thebottom face of the base plate 27 can easily and electrically beconnected to the circuit 43 on the top face of the base plate 27.

On the bottom face of the base plate 27, the resin plate 45 made ofnonconductive resin material is arranged to cover the capacitance sensor29. When the base plate 27 is faced to the ground so that thecapacitance sensor 29 correctly detects a capacitance change ε in theground, the resin plate 45 protects the capacitance sensor 29.

If the target buried object 19 is found in the ground, the buzzer 55immediately informs a worker of the presence of the target buried object19.

FIG. 8 shows a modification of the controller 49. In FIG. 8, partscorresponding to those of FIG. 6 are represented with like referencenumerals.

The controller 49A of FIG. 8 employs a voltage comparing circuit 69 anda reference voltage generating circuit 71 instead of the A/D convertingcircuit 63 and MPU 65. The capacitance sensor 29, an oscillating circuit59, a frequency voltage converting circuit 61, the voltage comparingcircuit 69, and the reference voltage generating circuit 71 form thecontroller 49A.

The reference voltage generating circuit 71 generates a referencevoltage to be compared in the voltage comparing circuit 69. Thereference voltage to be generated corresponds to a reference capacitanceε2 to be set. Accordingly, the reference voltage generating circuit 71of this embodiment serves as the reference value storing means.

The reference voltage generated by the reference voltage generatingcircuit 71 is sent to the voltage comparing circuit 69, which comparesit with a voltage change corresponding to a detected capacitance changeεs, and if a result of the comparison shows that εs is above ε2 likeFIG. 7, provides an output signal to the buzzer 55 through the drivingcircuit 67. Accordingly, this embodiment can also correctly detect thetarget buried object 19 and inform of the detection thereof with analarming sound from the buzzer.

According to the above-mentioned embodiments, the underground buriedobject detecting apparatus 1 is grasped by a worker and is handledthereby. Ends of the handling rods 9 a and 9 b may be attached to afront end of a traveling carrier, so that the detecting part 5 mayoverhang in front of the carrier and so that the constant height H iskept between the detecting part 5 and the ground 17.

In addition, the bottom face of the detecting part 5 may be providedwith a mat-like cushion that can disperse load. The mat-like cushion isset on the ground to keep the height H between the detecting part 5 andthe ground.

The information means mentioned above may be not only the buzzer 55 butalso a display that is arranged on the operation box 11, to display acapacitance change or a comparison result with numerals or graphs.

INDUSTRIAL APPLICABILITY

As mentioned above, the underground buried object detecting apparatusaccording to the present invention is appropriate to correctly detectthe presence of a target buried object in the ground according to acomparison of capacitance changes without regard to the material of thetarget buried object which may be made of, for example, resin.

1. An underground buried object detecting apparatus comprising: a baseplate; a capacitance sensor attached to the base plate to be faced tothe ground, to detect an underground capacitance change, the capacitancesensor having a measuring electrode in the form of a 360 degree annularring and a ground electrode in the form of a 360 degree annular ring,concentrically arranged on a bottom face of the base plate and definingan annular space therebetween; reference value storing means forprestoring a reference capacitance indicative of a detected capacitancewhen no target buried object is present in the ground; operation meansfor comparing a detected capacitance change with the referencecapacitance and detecting presence of a target buried object in theground; and information means for receiving a signal from the operationmeans and informing of the presence of the target buried object.
 2. Theunderground buried object detecting apparatus of claim 1, wherein themeasuring electrode and the ground electrode are each made of an annularconductive metal plate.
 3. The underground buried object detectingapparatus of claim 2, wherein: the capacitance sensor has integralterminals passing through the base plate; and the terminals areelectrically connected to a circuit arranged on a top face of the baseplate.
 4. The underground buried object detecting apparatus of claim 2,wherein on the bottom face of the base plate, a nonconductive resinmaterial is arranged to cover the capacitance sensor.
 5. The undergroundburied object detecting apparatus of claim 3, wherein on the bottom faceof the base plate, a nonconductive resin material is arranged to coverthe capacitance sensor.
 6. The underground buried object detectingapparatus of claim 1, wherein on the bottom face of the base plate, anonconductive resin material is arranged to cover the capacitancesensor.
 7. The underground buried object detecting apparatus of any oneof claims 1 to 4, 5 and 6 wherein the information means is a buzzer toreceive the signal from the operation means and inform of the presenceof the target buried object with a warning sound.